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Water Hyacinth: Available and Renewable resource

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Recently, attention is being devoted to the utilization of water hyacinth since the efforts to control plant growth by chemical; biological and mechanical means have met with little success. The real challenge is not how to get rid of this weeds but how to benefit from it and turn it into a crop. Thus the issue of water hyacinth should be looked from a different view. In this article the potential uses of water hyacinth are classified and discussed.

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									                          Water Hyacinth:
                  Available and Renewable resource
                             M.F.Abdel-sabour
                   Recycling and Environment consultant
                      E-mail: freemfs73@yahoo.com


Abstract:
    Recently, attention is being devoted to the utilization of water hyacinth
since the efforts to control plant growth by chemical; biological and mechanical
means have met with little success. The real challenge is not how to get rid of
this weeds but how to benefit from it and turn it into a crop. Thus the issue of
water hyacinth should be looked from a different view. In this article the
potential uses of water hyacinth are classified and discussed.
    Data indicated that the application of water hyacinth co-compost as soil
amendments especially to the sandy soils, can improve some soil hydro-
physical and chemical parameters and supplies the growing crops with several
nutrients. On the other hand, if the composted water hyacinth was collected
from a clean water bodies the levels of heavy metals would be lower than other
common organic fertilizers in the market.
    Water hyacinth removed various pollutants through the absorption and
uptake of toxic organic matter and heavy metals. Water hyacinth has drawn
attention as a plant of rapid growth and high biomass production, and capable
of removing pollutants from domestic and industrial waste effluents. Reduction
of heavy metals in situ by plants may be a useful detoxification mechanism for
phytoremediation. Therefore, water hyacinth could be employed for biological
treatment of contaminated water. Water hyacinth rhizomes and roots could help
in the removal of heavy metals from the aquatic habitat or constructed wet-land.
Therefore, it is undesirable to involve contaminated rhizomes and roots in
fodder or co-compost organic fertilizer. From these results the contaminated
water hyacinth may be dry ashed and heavy metals could be extracted and
recycled.

Background:
         Water hyacinth (Eichlorina cassipes (Mart. sol ms), was introduced to
Egypt in 1879, and was cultivated in ponds of public gardens, then it found its
way to water canals. Nowadays it is hardly possible to find a water habitat in
Egypt -particularly in delta- not menaced by this plant. Huge floating islands of
this weed mixed later with other sub-emergent and emergent aquatic weeds are
common in huge areas in Upper Egypt, Dammiata and Rossata branches of the
Nile, drainage canals as well as El-Manzalla Lake.
         The productive potential of water hyacinth is reported to be tremendous
Hussein, (1992) reported that in 50 days, a single plant produces 43 offsets
which produce 1894 offsets in another 50 days and after 200 days from the
start, one expects to have 3,418,800 new offsets. He indicated that about 20 dry
tons per hectare can be harvested from standing water hyacinth plants, wherease
a 5 to 8 harvests can be collected per year.
        Water hyacinth causes serious harms and has an adverse effect on water
resources, fisheries, irrigation, drainage canals and public health. (Hussein,
1992, Obeid, 1984; Batanouny and EL- Fiky, 1984 and Sculthrope, 1967)
        Methods to control water hyacinth can be classified into: chemical,
biological and mechanical methods. Chemical control methods depend on
several herbicides to control the plant. However, these methods have several
disadvantages such as the adverse effect on the environment and public health.
(Obeid, 1984) .the biological control methods on a trial bases have been carried
out to control water hyacinth using some pests as fungal pathogens, mites,
snails or insects and certain grass-eating fish species, however, the results were
not satisfactory. Moreover, introducing new pests to the environment may
disturb the natural balance and the biological diversity (Wright and Centor,
1984). Finally, several reports recommended the mechanical control methods
by using different machinery devices (e.g. mechanical mooring and rolling
machines, conveyers…ect.).
        Recently, attention is being devoted to the utilization of water hyacinth
since the efforts to control plant growth by chemical; biological and mechanical
means have met with little success.

                           Utilization of water hyacinth
        Utilization plans do not suggest the cultivation of the plant, since it is
considered as a pest. The real challenge is not how to get rid of this weeds but
how to benefit from it and turn it into a crop. The most important consideration
in the utilization of water hyacinth is its high growth rate and dry matter
production, there for the harvesting rate should equal to or more than the
growth rate. Several studies in Egypt and worldwide have been carried out to
investigate the efficient ways to utilize this weeds. In this article the potential
uses are classified and discussed.

1) Animal feed and animal production
         Trials employ water hyacinth for feeding cattle; goats, pigs and rabbits
have been carried out in several countries (Shoukry, 1982, El-Serafy et. al.,
1981, Osman et. al.,1981). The results showed that non-ruminants (pigs and
rabbits) can better utilize water hyacinth than cows and goats. The efficiency of
utilization was greater for rabbits. Several studies reported that dried water
hyacinth was successfully used in feeding poultry and ducks.
         Recently, Costa-pierce (1998) studied the feasibility of using a designed
integrated aqua culture-wetland ecosystem (AWE) for experimental food
production and inorganic nitrogen removal from tertiary-treated wastewater.
The AWE connected poly-culture aquaculture ponds with in-pond aquatic plant
systems (water hyacinths, Eichhornia crassipes, and Chinese water spinach,
Ipomea aquatica), a solar energy aeration system, and an artificial wetland.
Ponds were stocked with hybrid tilapia (Oreochromis mossambicus X urolepis
hornorum), common carp (Cyprinus carpio). Mosquitofish (Gambusia affinis),
and red swamp crayfish (Procambarus clarkii), and were flushed weekly with
new wastewater at 20%. Fish were fed a 32% protein floating ratio at 1% fish
body weight per day, and wheat bran was added at 1 mg 1-1 when water
conductivities exceeded 900 mmhos cm-1. Plants were allowed to grow until
they reached approximately 50% of the pond surface area, and then maintained
   at this area by manual harvesting. The results indicate that water hyacinth could
   play a significant role in wetland systems.

           Jantrarotai (1991) indicated that water hyacinth has potential as a
   roughage source for ruminants because its dry matter has high crude protein
   (18%) and low acid detergent fiber (33%) contents. However, the high moisture
   content of the plant (95%) may make their use as forage uneconomical. He
   reported that where grass crop (Ctenopharyngodon idella) were fed diets
   containing from 0 to 100% water hyacinth meal, weight gain, and protein
   efficiency ratio decreased as the amount of water hyacinth meal increased.

   2- Organic fertilizer (green manure or compost) or mulching materials:
           One of the important use of water hyacinth residues is as a compost and
   mulch (Mukhopadyay and Hossain, 1990), because water hyacinth contains
   high concentrations of plant nutrients such as N, P, Ca, Mg and K. Goel et. al.,
   (1989) Indicated that it concentrates these nutrients from water by factors
   ranging from 36 to 14000 folds. Table (1) shows the averages of common
   elemental content in water hyacinth tissues and its nutritional values (from
   several studies). The plant leaves were reported to contain 15.9, 13.9, 8.8 and
   8.5 mg of Ca, K, Mg, P and N per gram of dry weight, respectively. Also, the
   laminae had higher concentrations of K and P than the petioles (Oke and Elmo,
   1990). Water hyacinth would be very desirable to be used as a green manure
   since the release of the nutrients was reported to be easier, compared to other
   plants residues (Para and Hortenstine, 1974).

      Table (1) Nutrational and elemental content of water hyacinth tissues
          (general means from several studies on non-polluted plants.

                       Shoots               Roots                Whole plant
   Crude protein %     14.8                 9.3                  11.4
   Crude fiber %       15.6                 110.0                63.9
   Ash %               22.5                 49.6                 36.8
   Phosphorus %        0.5                  0.48                 0.51
   K%                  3.16                 0.83                 1.99
   Ca %                2.13                 3.27                 2.70
   Mg %                1.69                 2.77                 2.23
   Fe ppm              7854                 14825                10676
   Mn ppm              693                  2790                 1669
   Zn ppm              18.4                 93.6                 55.80
   Cu ppm              32.5                 53.5                 40.00
   Co ppm              10.8                 32.1                 21.40
   Cr ppm              31.8                 66.5                 49.00
   Ni ppm              2.5                  7.3                  4.90
   Cd ppm              0.7                  2.1                  1.60
   Pb ppm              26.9                 74.7                 51.21
   Hg ppm              0.2                  0.40                 0.39

1) Moreover, the tremendous amount of mechanically removed water
  hyacinth from water streams could be utilized as compost. Co-composts of
water hyacinth with other organic residues (crop residues, sewage sludge,
municipal solid waste … ect.) were found to increase the yields, protein and
neutron content of several crops (Singh and Yadav, 1986,Ahmed et. al.,
1992, Rabie et. al., 1995, Abdel-sabour and Abo El-Seoud, 1996). They
reported that single application of different tested composts had resulted in
a remarkable increase in dry matter yield, seed yields, protein content,
neutron content and chlorophyll in plant tissue (corn, sesame, sunflower,
and common bean. The results of Rabie, et. Al., (1995); Abdel-Sabour and
El-Seoud, 1996; Abdel-Sabour et. al., 1997, and Abdel –Sabour et.
al.,1997b, showed the superiority of water hyacinth compost compared to
other tested composts (sewage sludge or municipal solid waste co-
composts. Their data indicated that the application of water hyacinth co-
compost as soil amendments especially to the sandy soils, can improve
some soil hydro-physical and chemical parameters and supplies the growing
crops with several nutrients. On the other hand, if the composted water
hyacinth was collected from a clean water bodies the levels of heavy metals
would be lower than other common organic fertilizers in the market.

       Another potential usage was reported by Soerjaini, (1984). A substrate
from water hyacinth petioles mixed with rice barn and lime (100:10:5) and with
urea and phosphate fertilizers (up to 1.5% of medium weight) was composted
for 4-5 days, spread over shelves, sterilized and then used as substrate for
mushroom cultivations. This substrate gave after 10 days a very satisfactory
harvest, which ranged from 20 to 25% of the weight of the used substrate
medium.

3- Biogas production:
        In several countries water hyacinth is successfully used for biogases
production in fermentators of different capacities (Ikhtyar and Shamsuzzaman,
1984, Dhahiyat et al., 1984 and Haripada Sarker et. al., 1984). They concluded
that a mixture of 25% cow doing and 75% of dry water hyacinth yield best rates
of methane production. Their results indicate the huge potential of water
hyacinth as a non-conventional energy source. They estimated that one-ton of
dry water hyacinth could yield 370,000 L of biogas.

4- phytoremediation :
Water hyacinth has drawn attention as a plant of rapid growth and high biomass
production, and capable of removing pollutants from domestic and industrial
waste effluents. Water Hyacinth (Eichhornia crassipes) has demonstrated its
ability to remove nutrients and other chemical elements from sewage and
industrial effluents (Saltabas and Akcin, 1994). In their study, 10.00 ppm
chromium, 35.00 ppm copper and 14.00 ppm nickel solutions were used, and
absorption ability of water hyacinth was observed. Due to the positive
experimental results on the removal of chromium, copper and nickel, they
suggested that water hyacinth may be used for industrial effluents. Haselow et.
al., (1992) indicated that managed growth and harvesting of water hyacinth can
be utilized for water quality improvement in lakes, but only if the plants are
mechanically removed from the system. Aoyama and Nishizaki (1991)
evaluated the practical use of water hyacinth grown in natural water channels or
ponds for water purification. They recommended a shorter harvesting interval
to obtain more yield of the biomass. Jebanesan (1997) indicated that water
hyacinth was found to be more effective in the treatment of dairy wastewater.
The wastewater from a dairy was treated with the water hyacinth for a retention
period of 25 days, Water various physico-chemical parameters were analyzed at
0, 5,10, 15, 20 and 25 days after treatment. After the retention period of 25
days, water total solids, Ca, Mg and total hardness were reduced by 37, 5, 47.5,
54 and 33%, respectively. Water chloride, Cr, nitrous nitrogen, nitric nitrogen,
pH, alkalinity, COD, BOD, bicarbonates and specific conductance were also
reduced considerably than the control. In another investigation on natural
shallow eutrophicated wetland receiving influx of domestic sewage and
agricultural rub-off of the watershed, heavily infested with water hyacinth,
located in Ujjain city, Madhya Pradesh, State in India was studied (Billore et
al., 1998). The aims of the study were to determine the role of dense growth of
hyacinth in the removal of particulate matter attached to root system, and
nitrogen as contained in the root attached particulate matter (RAPM) and in the
plant tissue. The recorded hyacinth density was 79 plants per square meter with
1.549 kg dry plant tissue. They found that the plant in one square meter could
retain 663 g RAPM (about 42% of dry plant tissue), which potentially removed
upon the mechanical harvest of the plants on per meter square basis. In addition
to the significant amount of RAPM, the harvested hyacinth plant also brought
about removal of 1.396 g of organic matter, 0.536 g of total nitrogen, 0.482 g of
ammoniacal nitrogen, and 0.338 g of nitrate nitrogen per m2 waterscape basis.
In other words, when the hyacinth plants are manually/mechanically removed
from the wetland, potentiality of total nitrogen removal is 37.32 kg through the
plant tissue + 5.36 kg nitrogen/hectare in the RAPM, besides 6630 kg/h of
particulate matter through roots attachment (RAMP). The extensive root
systems of the hyacinth provide a huge surface area for attached particulate
matter and microorganisms, acting as ‘suspended sediment layer’ and rich in
nitrogen. Thus, for a eutrophicated wetland receiving wastewater rich in
particulate matter, the hyacinth growth has substantial potential for the removal
of particulate matter and nitrogen through their attachment to roots, in addition
to the nitrogen concentrated in the plant tissue.

         Another important usage for water hyacinth is its use as biological
treatment for raw sewage effluent. Ayade (1998) reported that pioneering
research efforts in the handling of municipal sewage in developing countries
have involved the use of water hyacinth to purify sewage for possible domestic
purposes re-use. The ability of water hyacinth to remove pollutant from raw
sewage effluent has been found to be impaired by sewage toxicity. Trials were
therefore carried out to adapt water hyacinth to toxicity and thereby increase its
ability to remove pollutants from raw sewage. The plants were adapted using an
active bio-degrader consisting of different bacteria species such as,
Pseudomonas aeruginosa, Escherichia coli, Klebsiella ozaenae, Klebsiella
edwardsiella and Baccillus subtilis. The adaptation progressed through 20, 40,
60 and 80% sewage dilution until plants capable of growth in 100% raw sewage
were obtained. Plants were observed for morphological growth and at four
weeks, samples were collected for tissue analysis. The plants progressively
absorbed nutrients from sewage up to the fourth week, when signs of toxicity
were observed (through wilting, loss of turgidity and reduction in leaf number).
However, plants that survived through a series of adaptations under various
sewage dilutions exhibited luxuriant growth on raw sewage. In synergy with the
active bio-degrader, the efficiency of the adapted water hyacinth to remove
pollutants (nutrients) from raw sewage was enhanced by 93%.

    I) Removal of heavy metals:
Water hyacinth (eichhorina cassipes) has drawn attention as a plant capable of
removing pollutants, including toxic metals from surface water (Kelly et al.,
1999). Reduction of heavy metals in situ by plants may be a useful
detoxification mechanism for phytoremediation Studies were conducted to
determine the phytotoxic effect and uptake capacity of heavy metals by water
hyacinth (Delgado et al., 1993, Akcine et. al., 1994, Abdel-Sabour et. al.,1996
and lytle et. al., 1998). Shine et. al., (1998) investigated lake Chpala, mexico
(1990-1991 ) historically the lake has received poorly characterized domestic,
industrial and agriculture wastes. Heavy metals (i.e. As, Cd, Pb, Cr and Zn)
displayed high levels during the dried seasons (presumably, due to high
evaporation). They reported high levels of both Cd and Pb, which were above
the chronic criteria according to EPA standards for protection of aquatic
ecosystem health.

A Study case:
    In a case study (unpublished data) the bioaccumulation of both Cd and Pb in
water hyacinth was investigated in greenhouse experiment. Plants were exposed
to water containing different levels of Cd ranging from 0 up to 20 ppm and its
possible combination with different levels of Pb ranging from 0 up to 100 ppm
in complete randomized blocks with three replicates. The aim of the study was
to determine the accumulation, translocation, interaction and removal capacity
of Cd and Pb by water hyacinth plants.

    The data showed that water hyacinth accumulated both Cd and Pb mainly in
the roots. No adverse effect or phyto-toxicity symptoms on plant were observed
due to increasing levels of both Cd and Pb in water. A positive significant effect
of tested element on its accumulation in different plant parts and simple linear
or polynomial regression equations between plant tissue content of element in
question and its levels in solutions were observed as shown in Figs (1-2). As it
could seen from the Figures roots retained higher levels of Cd or Pb than
leaves or stems. Cadmium content in whole plant was enhanced by both Cd and
Pb addition (synergetic effect) however, an antagonistic effect was noticed
between Pb whole plant content and Cd application.

    As shown in Table (2) the enrichment ratio (ER = metal content in treated
plant / metal content in control plant) varied widely according to plant part
(leaves, stems and roots) and tested metal interactions (Cd and Pb). The
application of Cd drastically increased Cd-ER ratios for all testd plant parts at
any levels of Pb. As expected the ER values were always higher in case of roots
> stems > leaves. Cd-ER ratios for whole plant showed a remarkable increase
up to 427 times than control treatment however, in case of Pb-ER ratios it was
only 40.78 times higher than its relevant treatment. It is worth mentioning, that
the increasing levels of Cd in solution reduced the value of Pb-ER ratio for any
tested plant part, which again confirm the antagonistic effect of Cd on Pb
uptake. The relative high increase in Cd-plant tissue compared to the
corresponding values for Pb-plant tissue (as determined by ER ratio) may
indicate the high plant affinity for Cd uptake. Delgado et al. (1993) indicated
that after 24 days of growth, Cd, Cr, Zn in water were depleted totally from the
nutritive solution suggesting complete absorption of these metals by the plants.

Table (2) Cadmium or lead enrichment in water hyacinth tissues as affected by
                            Cd and Pb treatments.

Cd rate mg/L      Plant part                    Pb rate mg/L
                                   0            5          50           100
Cd-ratio
0                L                 1            0.99        0.91         0.92
                 S                 1            3.01        1.22         1.14
                 R                 1            1.17        2.32         6.47
                 W                 1            1.13        1.18         1.34
5                L               12.10         10.82       12.92         8.31
                 S               38.87         32.36       32.36        21.79
                 R              295.90        308.10      326.40       409.30
                 W               59.08         58.24       62.00        68.05
10               L               17.58         35.02       32.01        42.65
                 S               51.13         60.57       60.47        58.11
                 R              547.20        535.90      596.20        652.8
                 W              100.70        112.10      306.30       132.00
20               L               34.52         40.36       73.42        97.03
                 S              133.90        127.40      131.40       126.40
                 R              1332.0       1579.00     1628.00      2642.00
                 W              243.20        279.00       306.3       472.90
Pb-ratio
0                L                  1         3.46          5.29        9.82
                 S                  1         1.52          3.34        7.09
                 R                  1         7.09         10.77       53.50
                 W                  1         5.99          9.41       40.78
5                L                0.92        2.34          4.15        6.73
                 S                0.41        1.46          2.99        4.23
                 R                0.51        6.73         10.51       41.40
                 W                0.63        5.73          8.91       31.23
10               L                0.49        2.29          4.63        6.70
                 S                0.31        1.40          2.96        4.15
                 R                0.49        6.39         10.19       41.20
                 W                0.51        5.25          8.78       30.87
20               L                0.48        2.11          3.99        6.59
                 S                0.27        1.33          2.87        4.09
                 R                0.49        6.29          9.91        41.1
                 W                0.51        5.13          8.44       29.79
    To evaluate the translocation of both Cd and Pb from roots to stems and
leaves, the ratio between total metal content in leaves divided by total metal
content in roots (L/R) was calculated and presented in Table (3). Similarly, total
metal content in stems compared by its relevant value in root (S/R) and sum of
L+S compared to R are presented in Table (3). The inspection of the Table
suggested that Cd is more mobile and could be translated form roots to leaves
and stems than Pb. Generally, Water hyacinth rhizomes and roots could help in
the removal of heavy metals from the aquatic habitat or constructed wet-land.
Therefore, it is undesirable to involve contaminated rhizomes and roots in
fodder or co-compost organic fertilizer. From these results the contaminated
water hyacinth may be dry ashed and heavy metals could be extracted and
recycled.

    Table (3) Cadmium or lead ratios in water hyacinth tissues as affected by Cd
                                  and Pb treatments.

Cd rate mg/L          Ratio                       Pb rate mg/L
                                     0            5          50            100
Cd-ratio
0                  L/R              1.05        1.02         0.84          0.35
                   S/R              0.96        0.71         0.77          0.33
                   L+S/R            2.02        1.73         1.62          0.69
5                  L/R              0.07        0.09         0.10          0.11
                   S/R              0.19        0.14         0.13          0.09
                   L+S/R            0.25        0.20         0.20          0.15
10                 L/R              0.05        0.06         0.07          0.06
                   S/R              0.14        0.13         0.16          0.12
                   L+S/R            0.26        0.22         0.22          0.19
20                 L/R              0.04        0.04         0.08          0.07
                   S/R              0.15        0.10         0.11          0.06
                   L+S/R            0.19        0.14         0.19          0.13
Pb-ratio
0                  L/R              0.07        0.06         0.07          0.02
                   S/R              0.22        0.05         0.10          0.03
                   L+S/R            0.29        0.11         0.17          0.06
5                  L/R              0.20        0.04         0.04          0.03
                   S/R              0.25        0.06         0.08          0.03
                   L+S/R            0.45        0.10         0.13          0.06
10                 L/R              0.11        0.03         0.06          0.02
                   S/R              0.20        0.05         0.10          0.03
                   L+S/R            0.31        0.09         0.16          0.05
20                 L/R              0.11        0.04         0.04          0.02
                   S/R              0.18        0.06         0.09          0.03
                   L+S/R            0.29        0.10         0.13          0.05

        Water hyacinth is not only capable to absorb and accumulate heavy
metals, but also it could tolerate its toxicity by converting it from chemically-
active toxic stat to inactive and nontoxic stat. Lenzi et al., (1994) evaluated the
removal of chromium (III) from aqueous solution by water hyacinth. The
results showed that there was good removal of Cr at rate of 10 mg Cr/1 solution
(the recovery was 87.52%), but for higher concentrations (50 or 100 mg/1), the
water hyacinth did not appear to be a good absorbent. It was also seen that,
higher rations of water hyacinth mass/solution volume lead to higher solution
decontamination. The absorption of Cr (III) by the water hyacinth was lower by
decreasing the pH solution. They indicated that Cr (III) removal by water
hyacinth was not influenced by the temperature in the range 17.5 to 26.0 degree
C, or by the dissolved oxygen concentration in the solution between 4.71 to
6.77 mg/l.

        Kelley et al., (1999) investigated the capacity of the water hyacinth to
remediate aquatic environments that have been contaminated with the
lanthanide metal, europium Eu(III). Using scanning electron microscopy (SEM)
they have been able to determine that Eu(III) is adsorbed onto the surface of
the roots and the highest concentration of Eu(III) was found on the root hairs. In
their study X-ray absorption spectroscopy (XAS) techniques were used to
speciate the Eu(III) adsorbed onto the surface of the roots. The XAS data for
Eu-contaminated water hyacinth roots provides evidence of a Eu-oxygen
environment wherease Eu(III) is coordinated to 10-11 oxygen atoms at a
distance of 2.44 Angstrom. This likely involves binding of Eu(III) to the root
via carboxylate groups and hydration of Eu(III) at the root surface.
Zhu et al., (1999) demonstrated the potential of water hyacinth for the
phytoremediation of six trace elements. These plants are being used
successfully for the phytoremediation of trace elements in natural and
constructed wetlands. The ability of water hyacinth to take up and translocation
six trace elements-As (V), Cd(II), Cr(VI), Cu(II), Ni(II) and Se (VI)-was
studied under controlled conditions. They indicated that water hyacinth
accumulated Cd and Cr at a higher levels, then Se and Cu at moderate levels,
however water hyacinth was a poor accumulator for As and Ni. The highest
levels of Cd found in shoots and roots were 371 and 6103 mg kg-1) dry wt.,
respectively, and those of Cr were 119 and 3951 mg kg-1 dry wt., respectively.
Cadmium, Cr, Cu, Ni, and As were more highly accumulated in roots than in
shoots. In contrast, Se was accumulated more in shoots than in roots at most
external concentrations. Water hyacinth had high trace element
bioconcentration factors when supplied with low external concentrations of all
six elements, particularly Cd (highest BCF = 2150), Cr (1823), and Cu(595).
They conclude that water hyacinth is a promising candidate for
phytoremediation of wastewater polluted with Cd, Cr, Cu, and Se. Therefore,
water hyacinth could be very efficient for phytoextracting trace elements from
wastewater containing low concentrations of these elements. Lytle et al., (1998)
Using X-ray spectroscopy, to show that water hyacinth, supplied with Cr (VI)
in nutrient culture, accumulated nontoxic Cr (III) in root and shoot tissues.
Their data indicated that the reduction of Cr (VI) to Cr (III) appeared to occur
in the fine lateral roots, then Cr (III) was subsequently translocated to leaf
tissues. Extended X-ray absorption fine structure of Cr in leaf and petiole
differed when compared to Cr in roots. In roots, Cr (III) was hydrated by water,
but in petiole and more so in leaf, a portion of the Cr (III) may be bound to
oxalate ligands. This suggests that E. crassipes detoxified Cr (VI) upon root
uptake and transported a portion of the detoxified Cr to leaf tissues. Cr-rich
crystalline structures were observed on the leaf surface. The chemical species of
Cr in other plants, collected from wetlands that contained. Cr (VI)-
contaminated wastewater was also found to be Cr (III). They proposed that this
plant-based reduction of Cr (VI) by E. crassipes has the potential to be used for
the in situ detoxification of Cr (VI)-contaminated wastestreams. Eichhornia
crassipes has been grown in the presence of a number of complexes of the
platinum group metals (Farago and Parsons, 1994). Those compounds that are
taken up by the plants in larger quantities are the more toxic one and they
reported the relative order of toxicities determined from visual appraisal and in
terms of oxidation states, to be Pt(II), Pd(II) > Ru(III) similar to Ru(II) similar
to Ir(III)> Pt(IV) similar to Os(IV)>> Rh(III). In most cases the metals are
accumulated in the roots, and where the toxic symptoms were observed when
the metal is translocated to the tops. Root elongation and biomass studies
confirm that Eichhornia is more tolerant to Rh(III) and Pt(IV) than to Pt(II).
Treatment with a Rh and three Pt complexes produced little differences in the
concentrations of Ca, Cu, Fe, Mn and Zn in treated plants compared with
controls. Sequential extractions of tissue from plants treated with [Pt(NH3)2Cl2]
showed that in the leaves and floats almost half the platinum is insoluble and
associated with alph-cellulose and lignin. They reported 16% of the metal was
removed by the enzyme pronase and can be considered to be associated with
proteins or amino acids. In the roots, about a third of the Pt is insoluble and
9.5% is removed by pronase. More Pt in the roots appeared in the fraction
containing water-soluble low molecular weight materials.

B- removal of organic contaminant:
        Water hyacinth was employed for wastewater treatment in many parts of
the world. By planting water hyacinth in wastewater pond, part of the gaseous
oxygen produced by photosynthetic activity of the green leaves is translocated
to the stems and roots and to the water body ; this oxygen is used by the aerobic
and facultative bacteria in biodegrading organic matter contained in the
wastewater. Two groups of bacteria normally exists in a water hyacinth pond
(WHP), namely the suspended bacteria which are present in the liquid portion
and the biofilm bacteria which are attached on the surfaces of the roots of the
water hyacinth plants and on the side walls and bottom layers of the pond itself.
Current design criteria for WHPs do not emphasize the roles of these two
groups of bacteria, but they are based on either empirical relationships or first-
order reaction rate and complete-mix flow condition. Chongrak and Raj (1998)
studied the significance of both the suspended and biofilm bacteria and the flow
hydraulics (based on dispersion number) in the reduction of organic matter in
the WHP system. Kinetic coefficient of the suspended bacteria was calculated
from a first-order reaction rate including the effect of organic loading rate. For
the biofilm bacteria, the reaction rate was also first-order and based on the
substrate flux into the biofilm. The integrated kinetic model proposed for the
WHP incorporates the activities of both the suspended and biofilm bacteria and
the hydraulic dispersion number. The model was found to be satisfactory in
predicting biochemical oxygen demand (BOD) removal in a full-scale WHP
treating an anaerobic pond effluent. The model is useful to achieve
improvement in BOD removal efficiency.
        Nor (1994) investigated the removal of phenols in the presence of
copper and zinc by Eichhornia crassipes was in order to assess its ability to
clean up industrial wastewaters. Results indicated that Eichhornia has
tremendous capacity to absorb phenolic compounds as well as Cu and Zn
simultaneously from test solutions containing these substances. The presence of
Cu or Zn resulted in decreased phenol uptake during the first 0.5 d, while the
presence of Cu and Zn in combination resulted in higher phenol uptake. After 1
d exposure, however, little or no differences could be discerned. Similarly,
absorption of Cu and zn in the presence of phenols did not seem to be adversely
affected by different combinations of Cu/Zn concentrations. In fact, some
synergistic effect could be detected between Cu and Zn absorption by
Eichhornia crassipes. Bioassays involving filtered Eichhornia root extract
indicated that phenol was also removed by the aqueous root extracts indicating
that cellular constituents of roots were involved in the process.

        Cyanide degradation by water hyacinths in solutions containing 3-300
mg/l cyanide was investigated in batch tests (Granato, 1993). Water hyacinth
was more efficient to remove free cyanide in the first 8 hours, compared to
cyanide controls (free of plant). Gold mill synthetic effluents containing free
cyanide (9 to 20 mg/l), thiocyanate (14 to 23 mg/l), and metallocyanides (iron,
copper and zinc) was fed to a continuous lab. Scale unit (61/h) to confirm the
ability of water hyacinth to degrade free cyanide and that it can remove zinc
and small amounts of iron. Copper and thiocyanate remained untouched in the
solution. Water hyacinth is only suitable to be used in conjunction with other
cyanide wastewater treatments.

    Water hyacinth can grow in oil-refinery wastewater after the water has
undergone an initial treatment of oil-separation, flotation and aeration (Tang
and Xian-wen, 1993). They indicated that the optimum COD under which E.
crassipes can be used to oxidize oil-refinery wastewater is between 65 and 131
mg/l and the highest possible COD is 262 mg/l. They reported that Eichhornia
crassipes, grown in two 3750-m2 oil-refinery wastewater oxidation ponds,
improved the quality and transparency of the outlet water. After 2 to 4 days
retention in oxidation ponds, turbidity decreased by 32%, phenol oil decreased
by 18%, COD decreased by 8-13%, nitrogen decreased by 6-18%, phosphorus
decreased by 12-24%, and several heavy metals decreased by 3-54% more than
the un-vegetated control. In addition, its oxygenated root zone helps to bring
about flotation and flocculation of oil residue, increased aerobic degradation,
and a large microbial population to stimulate decomposition.

Bio-sorption:
    Low et al., (1994) Reported the potential use of Biomass of non-living dried
water hyacinth roots (Eichhornia crassipes) for sorption of copper from aqueous
solutions. Maximum sorption was 20.90 mg Cu/g as determined for Langmuir
isotherm. Several factors affecting sorption were investigated. They include
effect of pH, initial concentrations, presence of chelators and other metals. They
suggested using this material in a packed-bed system for removing copper from
electroplating waste.
Biological indicators
    The water hyacinth samples collected from three Egyptian water bodies and
analyzed for major elements, essential and non-essential elements using prompt
gamma ray neutron activation analysis technique (PGNAA) to evaluate water
hyacinth as a bioindicator for pollution (Abdel-Sabour et. Al., 1996 and 1997).
Results showed that plant sample analysis showed good response to the heavy
metal pollutant level in water bodies. They suggested that there is a potential
use of such plant as a biological indicator. They indicate also, the biological
accumulation factor (BAF) has reflected the levels of pollutant in the
surrounding environment.

    Water hyacinth stems and leaves, have been successfully used as indicators
of heavy metal pollution in tropical countries (Gonzalez et al., 1989). They
reported that the uptake of heavy metals in this plant is stronger in the roots
than in the floating shoots.

     To study the bioconcentration of cadmium in water hyacinth, the plants
were exposed to water containing 2 mu g Cd (2+) /ml for extended periods of
time (Xiang et al, 1994). Three strains from several exposures during a 30-day
period were sampled for the analyses of cadmium and thiol group. The data
showed that the plant concentrates cadmium mainly in the roots and that the
cadmium uptake is proportional to the increase of the thiol group content. The
latter suggests the possibility of using the thiol group content to assess the
bioconcentration of heavy metal ions in water hyacinth and as a general
parameter for monitoring the heavy metal pollution of water.

                                 References

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                                                         Fig (1) Effect of Cd and Pb on Cd content in
                                                                 different plant tissue (mg/kg)
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                                               Fig (2) Effect of Cd and Pb on Pb content in different plant
                                                                      tissue (mg/kg)

								
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